The present invention relates generally to an apparatus for processing a substrate surface, and more particularly to such an apparatus that rotates a substrate, such as semiconductor wafer, glass plate, ceramic board or the like (hereinafter referred to generally as substrate), while supplying a processing solution, such as liquid photoresist, developing solution, etching agent, liquid dopant or the like (hereinafter referred to generally as processing solution), onto the surface thereof.
Apparatus of this general type have been broadly used in the art. One such apparatus is shown in Japanese unexamined laid-open application (Kokai) No. 59-90928, a typical illustration of which is shown in FIG. 3.
Referring to FIG. 3, the apparatus includes a rotary chuck 102 for holding a substrate 101 thereon and rotating it at a predetermined rate, a nozzle 103 disposed above the chuck 102 for supplying a processing solution onto the upper surface of the substrate, and a housing 104 provided in such a manner as enclose the substrate 101 therein.
The housing 104 defines a processing chamber, and the chamber is evacuated through an suction conduit 117 connected to a lower part of the housing, which is in turn connected with an exhauster (not shown). At the top end of the housing 104 there is provided an opening 105 in order to introduce air into the chamber in cooperation with evacuation by the exhauster. Surplus processing solution drains through a drain 114 which is also connected to the lower part of the housing.
Adjacent to the rotary chuck 102 there is provided a rectifying plate 107 in the shape of a flat ring having a declining peripheral edge. The rectifying plate 107 is mounted eccentrically to the chuck 102 so that the peripheral edge of the rectifying plate 107 sticks out biasedly to the portion to which the suction conduit 117 is connected.
Eccentricity of the rectifying plate 107 narrows a gap formed between the peripheral edge of the rectifying plate 107 and the inner surface of the housing 104, to increase the pneumatic resistance at that point so that processing of the substrate can be carried out uniformly throughout the entire surface thereof, e.g. in the case of forming a thin film of a photoresist, an even and uniform thin film can be obtained.
While the foregoing apparatus may be advantageous in terms of processing a substrate evenly and uniformly throughout the entire surface thereof, there are still some problems to be solved. That is, in the foregoing apparatus, since the gap formed between the peripheral edge of the rectifying plate 107 and the inner surface of the housing 104 is adjusted by eccentricity of the rectifying plate 107, the adjustment is difficult, though not impossible, and it requires the accuracy of production of the rectifying plate and the housing in order to control an air flow introduced into the processing chamber.
The foregoing apparatus has a disadvantageous structure that a processing solution is likely to enter the suction conduit 117. If a processing solution, particularly a liquid photoresist, adheres to and accumlates on the inner surface of the suction conduit 117, the conduit is narrowed and affect the air flow within the processing chamber.